1. Field of the Invention
The present invention relates to a method and apparatus for determining the vibration damping characteristics of an automotive component such as a brake structure, e.g. a brake pad or brake shoe.
2. Disclosure Information
Automotive brake systems present unique challenges to designers inasmuch as such systems must be capable of stopping a vehicle reliably during a long service life. Vibration-induced noise in disc brake pads is an issue which asserted itself since the dawn of the disc-brake age in the annals of mass produced automobiles.
The production of audible noise by automotive disc-brake systems is greatly affected by the presence (or absence) of self-damping capability offered by the disc-brake pads themselves. Not surprisingly, it is therefore desirable to produce pads having self-damping characteristics in the vibration regimes which would otherwise produce noise. The assessment of a brake pad's self-damping characteristics have been the subject of previous inventive activity. As a result, several test methods and types of apparatus have been proposed, such as that shown in U.S. Pat. No. 6,382,027. The method and apparatus of the '027 patent uses an exciter which is pulsed on and off, with the actual vibration damping being measured while the exciter is in the deactivated mode. This type of operation is not suitable for high speed assessment of parts because the vibration assessment must be accomplished serially. In other words, the vibration response is not measured while the exciter is providing vibratory energy to the disc-brake pad. Thus, more time is required to obtain the assessment. Moreover, the capabilities of the method disclosed in the '027 patent are wanting because of limitations inherent in the time decay process. Moreover, other test methods such as the Oberst Bar test are capable of measuring damping only at lower frequencies.
It is advantageous that a method and apparatus according to the present invention overcomes problems associated with prior art methods and apparatus for determining the inherent damping characteristics of automotive brake structures, including brake pads, as well as other components.